To depend on compiler flags, I do this: ## compiler_flags file keeps a copy of the compile flags $(builddir)/compiler_flags: force mkdir -p $(builddir) echo

To depend on compiler flags, I do this: ## compiler_flags file keeps a copy of the compile flags $(builddir)/compiler_flags: force mkdir -p $(builddir) echo '$(CPPFLAGS) $(CFLAGS)' | cmp -s - $@ || echo '$(CPPFLAGS) $(CFLAGS)' > $@ ##rebuild all objects if compile flags change $(LIBOBJECTS) $(RTLLIBOBJECTS) $(OPTLIBOBJECTS) $(TESTOBJECTS) $(builddir)/init_qt_workdir: $(builddir)/compiler_flags I"m pretty happy with the results.